When designing a building, one of the most crucial factors influencing energy efficiency is the site orientation. This refers to the positioning of a building in relation to the sun, wind, and surrounding environment. It determines how the building interacts with natural elements, which influences its energy performance throughout the year. Careful consideration should be given to each particular site. Factors such as local climate, topography, and surrounding buildings can impact the amount of solar exposure and wind patterns.
Low energy buildings can be achieved with many different orientations, however it is much easier if the building is positioned optimally on the site. Proper orientation can significantly reduce heating and cooling demands, enhance natural lighting, improve overall comfort, and reduce the reliance on artificial energy sources.
What is the best orientation for my building?
The ideal orientation (in northern hemisphere countries) is for the principal facade of the building to face 180 degrees due south. This is to make use of the solar energy during the heating season and maximise the use of the south facade. In winter the amount of heat required will be at its highest and the south facade will have the most opportunity to absorb solar radiation. Maximizing solar gain can significantly reduce heating costs. South-facing windows receive the most sunlight and large windows on this facade can let in heat during the day. Also, to avoid excessive heat loss, the building should have minimal openings on north-facing walls, as these receive little direct sunlight and are prone to heat loss.
It is also important to consider summer comfort. Minimising heat gain is essential in the summer to keep indoor spaces cool. Orienting a building with its longer sides facing north and south reduces direct sun exposure on east and west facades, which receive intense sunlight during morning and afternoon hours. Large east or west facing windows in particular can have a significant impact in terms of overheating and sun shading is essential for these orientations. South facing windows will generally also require some shading to ensure comfortable summer conditions. Shading devices such as overhangs, brise-soleil, pergolas, and nearby trees can block excessive solar heat gains.
Site orientation also plays a critical role in natural cooling. Buildings should be oriented to take advantage of prevailing winds, which can be channelled through openings to create cross-ventilation. Windows and vents placed strategically across opposite sides of a building allow for air movement, reducing the need for mechanical cooling.
Good orientation can also enhance natural lighting, reducing the reliance on artificial lighting during the day.
What if I can’t position my building optimally?
There may be situations where it is not possible to position a building optimally due to existing site constraints, or because it does not make the most of views and other site features. A low energy building can still be achieved but, for example, the fenestration may need to be designed differently or the building may need to have a more compact form. The Building Research Establishment states that a poor orientation can increase annual heating by at least a third. The most important thing to recognise is the optimum position is due south, and have a rational argument for any deviation.
By understanding and applying site orientation principles, architects can create energy-efficient buildings that enhance comfort while reducing environmental impact. Thoughtful planning at the outset of a project can lead to significant long-term savings and sustainability benefits.
Thinking Buildings are passionate about low energy building design and we also have our own certified Passivhaus designer. Please get in contact if you would like to know more or have any further questions.
